Media, such as, for example, speech, audio and video, delivered on packet (or frame) based communications networks are subject to packet loss that can affect the quality of media codecs (encoding/decoding systems). Although attempts are made to minimize the impact of these losses by, for example (in the case of speech), generating speech replacement material—these are known as Packet Loss Concealment (PLC) algorithms—the quality of the resultant reconstructed signals usually suffers nonetheless as a result of packet loss. Many compression codecs have built-in PLC algorithms, although one can bypass those algorithms to enhance performance, using instead PLC algorithms enhanced for loss characteristics typical of different networks. Predicting the quality of this multitude of combinations of codecs and PLC algorithms is a problem of general interest, since it is a necessary step in defining the Quality-of-Service (QoS) of packet systems, such as Voice-over-IP (VOIP) or IP (Internet Protocol) Video.
Differences in the quality of the codecs and PLC algorithms are due, in part, to differences in the amount of media content that is distorted when loss occurs. The rate of packet loss is commonly referred to as the packet loss rate (PLR). Quality-of-Service measurement schemes invariably rely on this measure to determine transmission quality. In fact, the use of PLR pervades the industry, from network measurement boxes to network planning algorithms, in both the voice and video domains.